The present application relates to disc brake assemblies, and more particularly, disc brake assemblies having tone rings connected thereto or otherwise associated therewith and methods for forming disc brake assemblies with tone rings.
Modern vehicles may employ an anti-lock braking system (“ABS system”) to increase the traction and control of the vehicle during adverse driving conditions. ABS systems prevent the wheels from locking by rapidly releasing and reapplying brake pressure. A typical ABS system includes sensors for monitoring the rotational speed and/or acceleration of each wheel of the vehicle relative to the other wheels of the vehicle. The ABS system may be actuated when the rotational speed or acceleration of one or more wheels is different than the rotational speed or acceleration of the other wheels.
The sensors may measure the rotational speed of a wheel by monitoring the rotation of the associated brake rotor. A brake rotor may be provided with an associated tone ring having a plurality of evenly spaced exciter teeth thereon in order to facilitate the measurement of rotational wheel speed. A sensor may be positioned adjacent to the tone ring to detect the change in magnetic flux caused by movement of the exciter teeth past the sensor.
Prior art attempts to provide brake rotors with such tone rings have presented numerous problems and disadvantages. For example, casting brake rotors with exciter teeth presents integrity issues resulting from the difficulty of obtaining close tolerances using a foundry casting process, as well as corrosion breakdown of the exciter teeth. Furthermore, cast-in teeth require the application of a costly rust-preventative coating.
To avoid the problems associated with casting exciter teeth into the brake rotors, tone rings may be formed separately from the brake rotors, then bolted onto the rotors. However, this requires the additional machining step of tapping holes in the brake rotor, forming the tone ring with fastening ears, and requires the additional component of a fastener for securing the tone ring to the brake rotor, thereby increasing costs and presenting reliability issues.
Simply press-fitting tone rings to the brake rotors also creates risk of failure. If different materials having different coefficients of thermal expansion are used for the tone ring and the brake rotor, the different rates of expansion of the two components when heated during operation may cause separation of the tone ring from the brake rotor.
Accordingly, there is a need for a new and improved disc brake assembly having a tone ring connected thereto.